This application describes a planned cohort study of 80,000 white and 45,000 black adult Seventh-day Adventists, enrolled from across the U.S. Questions not easily addressed by other study populations, can be answered. Taking advantage of the unusual dietary habits of Adventists, the special focus of this application is an association between soy intake, calcium intake, and cancers of the breast, prostate and colon. About half of black and white Adventists consume similar quantities of soy to that used in China or Singapore. Adventists also have a wide variance in intake of calcium. The increasing use of soy and calcium supplements by the American population needs further evidential support. Another strength of the proposed research is the proven ability to enroll and follow a large and cooperative cohort of black Adventists. The very high incidence and mortality ascribed to prostate cancer in black men may be associated with their dietary habits. Subjects will be enrolled church by church using a pretested plan whereby institutional media and respected members at individual churches promote the study. Subjects will complete a comprehensive questionnaire which is already developed and pretested. Cancer surveillance during follow-up will be by matching with state tumor registries where possible, matching with the National Death Index, and by obtaining and coding hospitalization records as necessary. Calibration studies in both black and white Adventists will allow bias correction. We believe that it is important to also gather blood, urine and subcutaneous fat from the subjects, and have a largely pretested plan to accomplish this. This will be further tested for feasibility at a location away from Loma Linda during Year 0 1 of the present study. The Adventist population has been cooperative with epidemiologic research for many years and has some unusual strengths as a research population, including the virtual absence of confounding by tobacco and alcohol, the wide range of dietary habits and the widespread use of soy products. They have made important contributions to the understanding of diet and chronic disease in the past. This larger study will provide much greater statistical power, more accurate and documented exposure assessment, and will also include a large cohort of black Adventists.